One of the most important structural features of the procaryotic cell is the cell walls, which confers rigidity and shape. The peptidoglycan layer as one of the important components of the cell walls is composed of two sugar derivatives: N-acetylglucosamine and N-acetylmuramic acid, and a small group of amino acids. The basic structure is a thin sheet in which the glycan chains formed by the sugars are connected by peptide cross-links formed by the amino acids. The full strength of the peptidoglycan structure is obtained when these chains are joined by peptide cross-links. The cross-linking occurs to characteristically different extends in different bacteria. In gram-positive bacteria, cross-linkage is usually by a peptide interbridge, the kinds and numbers of crosslinking amino acids varying from organism to organism.
The microbial cell wall lytic enzyme (mCWLE) capable of degrading the peptidoglycan structure of the cell wall can be divided into three groups:
1) the glycosidase capable of dissociating .beta.-1.4 linkage between polysaccharide chains, PA1 2) the acetyl-muramyl-L-alanine amidase capable of dissociating the peptide bonds between polysaccharides and peptides, PA1 3) the endopeptidase capable of breaking the cross-linking between polypeptide chains.
Until now, the study for mCWLE has been focused on the enzymes capable of dissolving Staphylococcus species resistant to lysozyme, fungi, or yeast.
These mCWLE are generally known to be possibly produced by culturing the strain of Streptomyces sp. including Str. griseus, Str. albus, Str. erythraeus, Str. rutergenesis, and Str. orientalis or other strains such as Staphylococcus aureus, Achromobacter lunatus, Bacillus subtilis, Myxococcus xantus, Pseudomonas aeruginosa and chlorapis sp.
These kinds of mCWLE can be used for preserving foods by adding them to foods, such as cheese, sausage, potato salad, and alcoholic drinks. Also, these enzymes are used for isolating cytosolic fraction of the microorganisms with treating them to remove the cell wall and further elucidating the cell structure thereof.